Lubricating compositions

ABSTRACT

Synthetic ester lubricants and certain organic sulfide loadcarrying additives form a synergistic mixture when added to mineral base oils, and there is a marked increase in the loadcarrying properties of the base oil.

United States Patent Forbes et al.

[4 1 Jan. 25, 1972 LUBRICATING COMPOSITIONS Eric Simon Forbes, Woking; Keith George Allum, Bagshot, both of England The British Petroleum Company Limited, London, England Filed: July 17, 1970 Appl, No.: 55,967

Inventors:

Assignee:

Related U.S. Application Data Continuation-impart of Ser. No. 700,022, Jan. 24, I968, abandoned.

Foreign Application Priority Data Jan. 31, I967 Great Britain ..4,58l/67 U.S. Cl. ..252/48.6, 252/56 R, 252/57 Int. Cl. t ..Cl0m 1/42, COIm 1/38 Field of Search ,.252/48.6, 45, 56, 56 S Primary Examiner-Daniel E. Wyman Assistant Examiner-W. Cannon Attorney-Morgan, Finnegan, Durham & Pine [5 7] ABSTRACT Synthetic ester lubricants and certain organic sulfide loadcarrying additives form a synergistic mixture when added to mineral base oils, and there is a marked increase in the loadcarrying properties of the base oil.

12 Claims, No Drawings which comprise synergistic mixtures of additives.

LUBRICATING COMPOSITIONS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 700,022, filed Jan. 24, 1968, now abancloned.

This invention relates to improvements in lubricating compositions; in particular it relates to lubricating compositions BACKGROUND OF THE INVENTION It is generally considered that load-carrying additives may be divided into two classes, namely antiwear and extreme pressure additives. When two lubricated moving surfaces are lightly loaded against each other, they are separated by an elastohydrodynamic oil film: as the load increases so the oil film thickness decreases. When the oil film thickness approaches the dimensions of the surface roughness, it will be penetrated by surface asperities: it is in this region that antiwear additives function by improving the oil film strength and thus reducing intermetallic contact. As the load is increased further, the bulk oil film collapses and antiwear additives are no longer sufficient to protect the surface. Extreme pressure additives function in this region by reacting with the metal surface to form an inorganic iron compound, such as iron sulphide, which prevents welding of the metal surfaces.

It is known to add certain esters to mineral oils to improve their load-carrying capacity (see, for example, the recent United Kingdom Pat. No. 1,047,493).

However, it was quiteunexpected to find that the addition of a small proportion of ester to a mineral oil containing a small proportion of a load-carrying additive augmented the additive response and indeed, caused certain additives, which previously showed no load-carrying activity at all, to improve the load-carrying capacity of a mineral base oil to a remarkable degree.

DESCRIPTION OF THE INVENTION This invention, therefore, provides an improved lubricating composition based on a mineral base oil and which contains up to 20 percent by weight of an ester and up to 20 percent by weight of a load-carrying additive.

Preferably the ester is a polyester containing two ester linkages per molecule, i.e., a diester. The most preferred diesters are those which are liquids or low melting solids.

Examples of suitable diesters are the compounds of the general formula AOOC-R-COOB Formula I wherein R represents a saturated hydrocarbon, i.e., alkylene, group having from 1 to 25 carbon atoms or a phenylene group and A and B are the sameor different and represent alkyl groups, each group containing from I to 10 carbon atoms, for example, diethyl sebacate. v

Other suitable diesters of Formula I are di-alkyl octadecanl,l8-dioate, di-alkyl-tetracosane-l,24-dioate, di-alkyl phthalate, di-alkyl adipate and di-alkyl sebacate, each of the alkyl groups containing from I to 10 carbon atoms.

Preferably the load-carrying additive is an organic disulphide, and the lubricating composition preferably contains 0.l to 10 percent by weight of the ester and 0.1 to 10 percent by weight of the disulphide.

Examples of suitable disulphides are the compounds of the general formula E-SSF Formula II wherein E and F are the same or different and represent alkyl, cycloalkyl, aryl, alkaryl or aralkyl groups, each of which may possibly be substituted by ester groups, and wherein at least one of E and F contains up to 20 carbon atoms. Preferably E and F are alkyl, cycloalkyl, aryl or alkaryl groups containing up to 10 carbon atoms each.

Suitable disulphides include di-n-butyl disulphide, di-cyclohexyl disulphide, 2,2'-(dicarboethoxy)diethyl disulphide, diphenyl disulphide and dibenzyl disulphide.

The mineral oil used depends on the use to which it is to be put and any lubricating oil can be used.

The lubricating composition according to the invention can also contain, if desired, other additives, for example, dispersants, detergents, viscosity index improvers, oxidation and corrosion inhibitors and pour point depressants. The lubricating compositions according to the invention can be used to lubricate, for example, automotive crankcases and transmission systems.

The invention also relates to a method of operating machinery wherein a lubricating composition based on a mineral base oil and which contains up to 20 percent by weight of an ester and up to 20 percent by weight of a load-carrying additive is used as the lubricant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is illustrated in the following table which compares a number of lubricating compositions according to the invention with reference lubricating compositions. In most cases the lubricating composition according to the invention contain equivalent molar quantities of ester and load-carrying additive. Tests on the various compositions were carried out using a Shell Four-Ball Machine.

The antiwear test was carried out under a load of l 5 kg; at a running speed of 1,500 revolutions per minute, and wear scars on the balls were measured after 30, 45 and minutes, respectively.

Using such conditions of light loading and long running times the test measures antiwear, rather than extreme pressure properties of the compositions. E. R. Braithwaite, Lubrication and Lubricants," Elsevier Publications, 1967, p. 42.

TAB LE Anti-wear test, wear scar diameter Coneenin mm.

tration,

weight 30 45 60 Compound percent Base 011 min. min, min.

1 Liquid .59 .72 81 Anti-wear test, wear scar diameter Concenin m.m. i i a 45 60 we g it Compound percent Base oil mln. min. min.

[)lothyl sebacate.... 1.104 "d m 7 63 J33 Dl-n-butyl disulphide. 0.821} O 17 {1)1cthylse1mcate.... dn, .511 .71 .1 Dl-n-hutyl dlsulphlde. 0.410 (3 n T, 18... Dl-cyclo hoxyl disulphide... 4.200 .do. l I m {Niothyl sebucnto. 4.745} 40 51 DI-cyclo-hcxyl disulphide... 260 a I T 20".. (-S-CIIz(1llzCOOEt)z- .go. 2 A" 21. .do .a ..do... .1 .55 .m 22.... .do. 0.011I 0.... l)lcth vl solmcalm 4. 775 50 H i {(S(/l1 (.|11(()()Ei)z Dlcthyl Selim-nit... r. .41 (SCllg(lll (l()()El.)z 4 Nlnthyl sohacnto. 1 I 4 '4" -s (:n2-om-ooom 1 3 Dluthyl sebacate 7 A5 .51 I i(s-om cn2*r:oom 0.017} 27.. Dlphonlyl iilsulphldofl .do .44 .47 .5 I) othy so )acate. 7 A0 38 40 {Dlphonyl disulphide. 4. 037} I, 20.. Dlbenzyl disulphide. 4. 558 do .48 .5- .56 {Dlethy1sebacate 4.775} d0 .38 A4 .4" Dlhenzyl disulphide 4.558

Di-lso-octylsebaeute 10.000 do .66 .75 .81 {Dl-lso-octyl sebacate 10. 000} do 33 I 37 43 Dlphenyl disul hide 4.037 r 33 Dlmethylocta ocan118 6.340 do .552 .633 .085

dioate. Dlmethyl octadecan 1-18 6. 340 34 oate. .do .434 .451 .511

Dl-n-butyl disulphide"... 3. 296 35 Dicmethyl tetracosano 1-21 7. 800 d .59, 62 .5114

date. Dlmethyl tetracosane 1-24 7 800 H 36 dloate. ..d0 .455 .4110 n) Dl-n-butyl dl5\l1')hid i D moth locta ecan i. 37 dloate? do .344 .383 .445

Dlphenyl disulphide... 4.037 l 38 gimetlliyl 9291318310... ..do .631 .111 1.15 met y p ha ate... I 518 """"'{Dl-n-butyl disulphide. 3.2%} 40 Slethylaflipafie. .do. .640 .720 .820

ethya pae.. 1 41 "iDl n-butyl disulphide... 3. 2%}- 42 Bifilyl .....do. .578 .620 .020

-ay sph 43 "{Dlethyl sebacate 4. 775}- '2, 2' dlcarboethoxy) diethyl disulphide it is seen that increasing the amount of ester in the base oil/ester composition can worsen the antiwear result. This is demonstrated by compositions Nos. 2-9 of the table, composition No. 2 being considerably worse than No. 3 and worse than any of the other results.

in composition No. 31 it can be seen that the antiwear performance of the ester plus base oil composition at a 10 percent concentration of ester is worse than that of the base oil alone.

With regard to the disulphide component, di-n-butyldisulnearly equal total concentrations of additives are below the levels attained with the corresponding blends containing either component alone.

In addition it is seen that in compositions Nos. 40 and 41, the blend of diethyl adipate and base oil has worse antiwear performance than the base oil alone, as has the disulphide alone, compositions Nos. 10-13, yet when they are mixed together, they bring about a marked improvement in wear resistance.

We claim:

1. A lubricating composition which comprises i. a mineral oil in major amount;

ii. up to 20 percent by weight of a diester of the general forphide, as is shown in compositions Nos. 10-13, leads to conmula siderably worse antiwear performance than the base oil at all AOOCR--COOB 322 2233283252? though it is known to have extreme wherein R is a saturated alkylene group of from 1 to 25 carbon atoms or a phen lene grou and Thus It can be .concluded that composmon for ex- A and B, independently, a re alkyl of from 1 to 10 carbon ample, has an antiwear performance unexpectedly better than atoms and h beStdieter/b2.1se comPgsition. and better than the g iii. up to 20 percent by weight of an organic disulphide load di-n-butyl disulphide COmPOSIIIOIL IIlS unexpected to find th s carrying additive, Said organic disulphide being of the degree of performance because it 18 not possible to obtain general formula such low antiwear results using any amount of diethyl sebacate or di-n-butyl disulphide by themselves.

With regard to the other data in the table, it can be seen h i E nd F, independently, are alkyl, cycloalkyl, from compositions Nos. 18, 19, 27 and 28 that the presence of ryl, alkaryl, aralkyl and ester-substituted such groups diethyl sebacate can produce an antiwear result when added d in conjunction with the disulphide considerably better than wherein at least one of E and F contains from 1 to 20 carthat of the organic disulphide by itself. bon atoms, the amount of said diester and disulphide in Further unexpected results are shown in compositions Nos. said composition each being in the range of from at 4, 21 and 26. In No. 4, 1.194 percent weight of diethyl least sufficient to impart a marked, synergistic increase sebacate is used, in No. 21, 1.23 percent weight of 2,2'-(dicarin the load carrying properties of said oil to 20 percent boethoxy)diethyl disulphide is used. As can be seen, the wear 7 5 by weight.

scar diameters for the mixture of diester and disulphide at very 2. A lubricating composition which comprises i. a mineral oil in major amount;

ii. from 0.1 to percent by weight of a diester selected from di-alkyloctadecan-l,l 8-dioate, di-alkyl tetracosanel ,24-dioate, di-alkyl phthalate, di-alkyl adipate or di-alkyl sebacate, each of the alkyl groups containing from I to 10.

carbon atoms, and

iii. 0.] to l0 percent by weight of an organic disulphide selected from di-n-butyl disulphide, di-cyclohexyl disulphide, diphenyl disulphide, dibenzyl disulphide or 2,2- (dicarboethoxy)-diethyl disulphide.

3. A composition as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is di-n-butyl disulphide.

4. A composition as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is di-cyclohexyl disulphide.

5. A composition as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is 2,2-(dicarboethoxy)- ilielhyl disulphide.

(a. A cumpnuilimt as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is diphenyl disulphide.

7. A composition as defined in claim 2 wherein said diester is di-iso-octyl sebacate and said disulphide is diphenyl disulphide.

8. A composition as defined in claim 2 wherein said diester is dimethyl octadecan-l,l8-dioate and said disulphide is di-nbutyl disulphide.

9. A composition as defined in claim 2 wherein said diester is dimethyl tetracosan-l ,24-dioate and said disulphide is di-nbutyl disulphide.

10. A composition as defined in claim 2 wherein said diester is dimethyl octadecanl l 8-dioate and said disulphide is diphenyl disulphide.

11. A composition as defined in claim 2 wherein said diester is dimethyl phthalate and said disulphide is di-n-butyl disulphide.

12. A composition as defined in claim 2 wherein said diester is diethyl adipate and said disulphide is di-n-butyl disulphide.

l l I 

2. A lubricating composition which comprises i. a mineral oil in major amount; ii. from 0.1 to 10 percent by weight of a diester selected from di-alkyloctadecan-1,18-dioate, di-alkyl tetracosane-1,24-dioate, di-alkyl phthalate, di-alkyl adipate or di-alkyl sebacate, each of the alkyl groups containing from 1 to 10 carbon atoms, and iii. 0.1 to 10 percent by weight of an organic disulphide selected from di-n-butyl disulphide, di-cyclohexyl disulphide, diphenyl disulphide, dibenzyl disulphide or 2,2-(dicarboethoxy)-diethyl disulphide.
 3. A composition as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is di-n-butyl disulphide.
 4. A composition as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is di-cyclohexyl disulphide.
 5. A composition as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is 2,2-(dicarboethoxy)-diethyl disulphide.
 6. A composition as defined in claim 2 wherein said diester is diethyl sebacate and said disulphide is diphenyl disulphide.
 7. A composition as defined in claim 2 wherein said diester is di-iso-octyl sebacate and said disulphide is diphenyl disulphide.
 8. A composition as defined in claim 2 wherein said diester is dimethyl octadecan-1,18-dioate and said disulphide is di-n-butyl disulphide.
 9. A composition as defined in claim 2 wherein said diester is dimethyl tetracosan-1,24-dioate and said disulphide is di-n-butyl disulphide.
 10. A composition as defined in claim 2 wherein said diester is dimethyl octadecan-1,18-dioate and said disulphide is diphenyl disulphide.
 11. A composition as defined in claim 2 wherein said diester is dimethyl phthalate and said disulphide is di-n-butyl disulphide.
 12. A composition as defined in claim 2 wherein said diester is diethyl adipate and said disulphide is di-n-butyl disUlphide. 